package problem516;

//516.最长回文子序列
//https://leetcode.cn/problems/longest-palindromic-subsequence/description/

class Solution {
    public int longestPalindromeSubseq(String s) {
        int n = s.length();
        int[][] dp = new int[n][n];
        for(int i = n-1; i>=0; i--) {
            for(int j = i; j<n; j++) {
                if(s.charAt(i) == s.charAt(j)) {
                    if(i == j) dp[i][j] = 1;
                    else if(i+1 == j) dp[i][j] = 2;
                    else dp[i][j] = Math.max(dp[i][j], dp[i+1][j-1]+2);
                }else {
                    dp[i][j] = Math.max(dp[i][j-1], dp[i+1][j]);
                }
                // System.out.println(i + " " + j  + " " + dp[i][j]);
            }
        }
        return dp[0][n-1];
    }
}

/*

dp[i][j]:i~j之间的最长回文子序列的长度
01234
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*/